hypervisor: Add pause/resume definitions to VM trait

Add Pause/Resume functions for VM trait. For KVM it
will be empty implementations. For MSHV it needs to freeze
and unfreeze the partition.

Signed-off-by: Muminul Islam <muislam@microsoft.com>

hypervisor/src/vm.rs

@@ -390,6 +390,16 @@ pub trait Vm: Send + Sync + Any {
     ) -> Result<()> {
         unimplemented!()
     }
+
+    /// Pause the VM
+    fn pause(&self) -> Result<()> {
+        Ok(())
+    }
+
+    /// Resume the VM
+    fn resume(&self) -> Result<()> {
+        Ok(())
+    }
 }
 
 pub trait VmOps: Send + Sync {